The link style suspension system represents a common type of suspension system utilized on vehicles equipped with a solid or beam axle. The link style suspension system offers a compliant and well-functioning method of mounting/suspending the axle to the vehicle; and, involves several different links, including upper control links, lower control links, and usually a lateral stabilizing device such as a Panhard or track bar. The combination of these links enables the axle to travel and articulate rather freely, while still providing a relatively stable platform for the vehicle to be suspended on.
The Panhard bar can lead to deficiencies in suspension and steering systems, particularly when the Panhard bar is oriented alongside the draglink. When the vehicle encounters a road obstruction, the control links react to the obstruction by allowing the axle to either compress upward closer to or extend away from the vehicle frame, the reaction causing: First, the Panhard bar arcs upwards or downwards, respectively, thereby exerting a lateral force on the axle perpendicular to the direction of the vehicle. Since the wheels are attached to the axle and planted on the ground, the lateral force acting on the axle is translated to the vehicle body which responds by moving perpendicular to the direction of the vehicle. This translational motion is bump-induced yaw. Second, when the endpoints on the Panhard bar fail to coincide with the endpoints on the draglink, the Panhard bar and draglink move through different arcs. The differing arcs serve to turn the steering knuckles even though the steering wheel is not turned, this unintentional turning is known as bumpsteer.
Bumpsteer and bump-induced yaw both contribute to an uncomfortable ride and make a vehicle handle poorly. Bumpsteer can be minimized by designing the steering system to transmit steering input from the frame to the axle with mechanical linkages that substantially coincide with at least one of the suspension control links. Bump-induced yaw can be eliminated with methods that center the axle beneath the vehicle throughout suspension travel: one method involves replacing the Panhard bar with another type of lateral stabilizing device, e.g., a Watts link; a second method involves using a suspension system that does not require a lateral stabilizing device, e.g., a triangulated 4-link suspension system.
The triangulated 4-link suspension system is a link-style suspension system that uses only four control links to completely locate the axle fore and aft and side-to-side beneath the vehicle throughout suspension travel. In particular, the angling of at least two of the four control links keeps the axle centered beneath the vehicle throughout suspension travel thereby controlling the side-by-side motion of the axle. Therefore the angulation of the control links serves the same purpose as does the lateral stabilizing device and eliminates the need for the lateral stablilizing device in the triangulated 4-link suspension system; a quality unique to the triangulated 4-link suspension system among all other link-style suspension systems (except the wishbone 3-link). The triangulated 4-link suspension system has seen extensive service as a rear suspension system on production based vehicles, for example on General Motors' G-Body cars from 1978-1988 and Ford's Fox platform vehicles. Although widely respected as a rear suspension system, the triangulated 4-link suspension system is unknown as a front suspension system for production based vehicles.
Most of this neglect of the triangulated 4-link suspension system as a front suspension system appears derived from automobile manufacturers trending away from beam axle front suspension systems and toward independent front suspension systems. However, part of this neglect is likely due to packaging constraints. The configuration of the angled control links in the triangulated 4-link suspension system requires ample space within the frame for proper installation and operation. Much of the area forward of the firewall is occupied by the engine and its attendant cooling, electrical, and control systems, thereby leaving little free space to accommodate the angled control links in a triangulated 4-link suspension system. Given that Ford's Super Duty trucks, Dodge's Ram heavy duty trucks, and Jeep's Wrangler utility vehicles are all produced with a solid front drive axle (when equipped), that the front suspension systems on all these vehicles include a Panhard bar, the deficiencies surrounding the Panhard bar as discussed above, and the continued strong demand for these vehicles by the public, then clearly a triangulated 4-link suspension system that can be incorporated into the front end of these vehicles would greatly benefit the automobile manufacturers, light pickup truck/utility vehicle market, and motoring public. The present invention represents a triangulated 4-link suspension system and associated steering system specifically designed to address these issues.